Serena Williams is out of Wimbledon after a fourth-round loss to Sabine Lisicki. / Ben Stansall, AFP/Getty Images

by USA TODAY Sports, USA TODAY

by USA TODAY Sports, USA TODAY

WIMBLEDON, England - Serena Williams' loss Monday to Sabine Lisicki in the fourth round was the latest shocker in an unpredictable Wimbledon.

But it happens, says Patrick Mouratoglou, one of Williams' coaches.

"She's human," he said, following the world No. 1's 6-2, 1-6, 6-4 loss to the No. 23 seed from Germany. "You cannot expect for anybody even if she is the greatest player of all time, if she is, to be perfect on all the matches all the year. She is not, and she will never be.

"I think still that her low level is better than it was before. But she is a human. She is going to lose some matches, and we have to be ready for that."

Williams, too, suggested that maybe shocked is the wrong word to use.

"It's not a shock," Williams said. "Like I said, she plays really good on grass. She has a massive, massive serve. So going in there you have to know that it's definitely not going to be an easy match playing her at Wimbledon, especially on Centre Court.

"It's definitely not a shock."

Even so, most observers were surprised, particularly in how it happened.

Williams won nine consecutive games in the middle of the match and was up 3-0 in the third set. Twice she was up a break, but she couldn't close.

Mouratoglou suggested fatigue was a factor.

"Maybe she is a bit tired," he said. "That is a possibility. She had one day like that at Roland Garros against (Svetlana) Kuznetsova. For me it was the same kind of day. She went through (in Paris). After she played great until the end of the tournament and she won it. If she would have found a way to win (Monday) probably she would have won the tournament and we wouldn't be wondering those questions.

"... When you don't feel your game it's more difficult and maybe she was tired. I don't know exactly. Today she couldn't find a way to win the key points of the match."

Mouratoglou, who has been linked romantically with Williams (though neither will discuss it), expects Williams to bounce back.

"When she loses she is even more motivated to work hard," he said. "It's bad news for the opponents."